Foamy and then flat and sweet

So I've had a reoccurring issue with my last few extract brews. I'm following the instructions laid out with the brew kits exactly and make sure everything is very clean. My end results have been a very foamy beer when I first open and pour, but then the head settles out and it's very flat. Now, I can still see quite a bit of carbonation coming up from the bottom of the glass, but the surface doesn't show that. The taste is decent, but it's always too sweet and flat tasting. The most recent brews I have done are a dark coffee/chocolate ale, scotch ale, and a Shiner clone if that helps/makes a difference. Please lend me your collective knowledge.

 

How long are you letting these beers ferment? The fact that you are getting excessive foaming and then the sweetness makes it sound like primary fermentation is not complete by the time you bottle the beer. This would cause the beer to continue fermenting in the bottles which would be causing the foaming. It would also explain why the beer tastes sweet since the yeast would not have finished up - leaving more residual sugar than should be in there.

 

I'm letting them ferment for at least 2 weeks in the primary. Then another 2 weeks in the secondary. This is usually - the Scotch ale was longer because it was a higher ABV. I agree with what you say about primary fermentation not completing as I had that same thought. I'm following the instructions provided, but I'm not confident in judging when that primary fermentation has completed.

 

Two weeks in the primary sounds pretty good provided that the yeast is viable enough to ferment completely. I don't do a secondary so I can't speak to that. It sounds like you don't have a hydrometer if you are not confident that primary fermentation has completed. I would suggest you get a hydrometer and start taking readings after 2 weeks in the primary and see where your gravity is. That would give you a better idea of whether the beer is completely finished or not.

 

+1. It sounds like you're attenuation is low despite the length of time in primary. Same thing happened to my second batch (what was supposed to be an Imperial Nut Brown). I would check how well you're aerating the wort before pitching yeast, fermentation temperature (mine was too high for that batch, so I started building my fermigerator), possibly look into a yeast starter (very easy but some kits wont recommend it in the instructions).

 

it would be helpful to know your og & fg.
if you didn't take measurements, what numbers did the kits predict?
temp you are fermenting at?
& how are you priming, batch or individually?

 

It would take 15 - 18 beers in order to pinpoint the exact cause of your problem...I mean, I could ya' know...kinda help you with that and stuff...